1. Field of the Invention
The present invention relates to ciphering data, and more particularly to a system and method for controlling the ciphering of voice, data, and/or other types of call information in a mobile communication system.
2. Background of the Related Art
In a GSM (General Systems for Mobile communication) mobile communication system, which performs 2-generation commercial services and a 2.5 generation GPRS (General Packet Radio Service) commercial services in the U.S.A or Europe, a user authentication process and a ciphering activation process are performed. These processes require registration procedures which allow the user of a mobile terminal to notify a network that the user will always use the terminal whenever the terminal is powered on. The registration procedures include an attach registration procedure, a location area update registration procedure, and a routing area update registration procedure.
In the course of performing registration procedures, the user authentication process and ciphering activation process are carried out when required by the network. More specifically, when a mobile communication terminal requests registration to the network, the network performs the user authentication process of confirming whether the terminal is an authenticated terminal. The ciphering activation process then determines whether data to be transferred between the terminal and network should be ciphered.
The user authentication and ciphering activation processes prevent wireless voice or data from being wiretapped or abused by a third party. Once the ciphering activation is set up between the mobile communication terminal and the network through the ciphering activation process, the call information is ciphered and then transferred therebetween.
Two methods may be used to determine whether ciphering should be carried out. In the first method, whether or not ciphering should be performed is determined in the course of registering the mobile communication terminal to the network after the terminal is powered on. In the second method, whether or not ciphering should be performed is determined when the mobile communication terminal wants to perform a specific service. The specific service includes a voice call for talking over the telephone, an SMS (Short Message Service) for transmitting a short message, an SS (Supplementary Service), a PDP (Packet Data Protocol) context activation service for transmitting a GPRS packet, etc.
Even when the data transfer procedures are not promised between the mobile communication terminal and the network (that is, even when the ciphering activation process is not carried out in registering the mobile communication terminal to the network and the data is transferred without ciphering), the ciphering activation process can be carried out by the network at the time of executing a service. In so doing, the data is ciphered and transferred from that time point.
FIG. 1 shows a general configuration of a mobile communication system which ciphers data transmitted using the GSM standard. This system comprises a mobile communication switching center 150 connected to a public switched telephone network (PSTN) and/or an integrated services digital network (ISDN) 160 for connection to a computer 180 through a general wire phone 170, or for direct connection to the computer, a plurality of base station controllers 130, 140 connected to the mobile communication switching center 150, a plurality of base stations 111, 121 respectively connected to the base station controllers 130, 140, and a plurality of mobile communication terminals 110, 120 respectively connected to the base stations 111, 121 through wireless links.
The base stations 111, 121 convert signal formats for wireless and wire links between the mobile communication terminals 110, 120 and the mobile communication switching center 150. The base stations also measure a transmitting/receiving electric field strength (signal intensity) of the terminals and transmit this information to the switching center 150.
The base station controllers 130, 140 serve as connection means between the respective functions by elements in the plurality of base stations 111, 121 and cell operators. The base station controllers also perform functions such as operational management of the base stations, management of service conditions of hardware and software in the base stations, assignment and construction of resources with respect to call traffic, establishment of information on operations of the base stations, operation and monitoring of the base stations, monitoring of sub-equipments associated with failure, etc.
The switching center 150 provides a line switching service to the base station controllers 130, 140 and the mobile communication terminals 110, 120, and performs a channel handoff as an additional function. In the mobile communication system described above, when any user transmits or receives a call using terminals 110, 120, the terminal is connected to a respective one of the base stations 111, 121.
FIG. 2 shows a flow of messages between a mobile communication terminal and a network for a related-art ciphering activation process, which may be performed in the GSM mobile communication system shown in FIG. 1.
In GSM and GPRS commercial services provided in Europe, when a mobile communication terminal 10 is powered on, the terminal requests registration to a network 20. At that time, the terminal transmits a registration request message (Attach Request) 201 to a base station through a wireless link, and the base station transmits the registration request message 201 to a mobile communication switching center through a base station controller.
The network 20 receives the registration request message 201 from terminal and determines whether a ciphering activation process should be performed. When it is determined that the ciphering activation process should be performed, the network transmits a ciphering authentication request message 202 to the terminal 10. This terminal then transmits a ciphering authentication response message 203, suitable for the ciphering authentication request message 202 from the network, to the network.
When the network receives the ciphering authentication response message 203 from the terminal, the network transmits a registration completion message 204 indicative of completion of the registration procedure to the terminal, and thus the ciphering activation process between the terminal and network is finished.
When it is determined that the ciphering activation process should not be preformed by the network, the network does not transmit the ciphering authentication request message to terminal. Thus, data is transmitted between the terminal and network without being ciphered.
FIG. 3 shows the flow of messages for ciphering a voice call in accordance with a related-art process, which may be performed in the GSM system shown in FIG. 1. When terminal 10 transmits a connection management (CM) service request message 301 to the network 20 in order to transmit a voice call, the network determines whether or not a ciphering activation process should be preformed in response to the CM service request message 301. When it is determined that the ciphering activation process should be performed, the network transmits a ciphering authentication request message 302 to the terminal.
The terminal transmits a ciphering authentication response message 303 suitable for the ciphering authentication request message 302 transmitted from the network 20, and thus the ciphering activation process between the terminal and network is finished.
When the network receives the ciphering authentication response message 303 from the terminal, the network transmits a CM service registration completion message 304 indicative of completion of the registration procedure to the terminal.
The related-art processes described above with reference to FIGS. 2 and 3 will be described again with reference to FIG. 4. When a GSM-type mobile communication terminal is powered on and is in a wait state 401, the terminal transmits a registration request message associated with data or a CM service request message associated with a voice call to a network. The network receives the message, 402, and determines whether a ciphering activation process should be performed or not, 403.
When it is determined that the ciphering activation process should not be performed, the network transmits a registration/CM service completion message indicating that the ciphering activation process should not be performed to the mobile communication terminal, 404. Thus, the procedure is finished without performing the ciphering activation, 405. Then, all data to be transmitted after the procedure is transmitted without being ciphered.
When it is determined that the ciphering activation process should be performed, 403, the network generates a RAND (RANDom number) value to compute/store an SRES (Signed RESponse) value, 406. The network then transmits a ciphering authentication request message to the terminal, 407.
The terminal receives the ciphering authentication request message from the network and transmits a ciphering authentication response message to the network. Then, the network receives the ciphering authentication response message from the terminal, 408, and compares an SRES value transmitted from the terminal with the SRES value stored in the network to determine whether the two values are equal, 409.
When it is determined that the two values are not equal, 409, the network transmits a registration/CM service unavailable message indicating that the registration/CM service will not be used any more to the terminal, 410, and then the procedure is finished, 411. After the above procedure is finished, the transfer data cannot be subjected to the ciphering service.
When it is determined that the two values are equal, the network transmits a registration/CM service available message indicating that the registration/CM service will be used for the terminal 412, and then the procedure is finished, 413. After the above procedure is finished, the transfer data can be subjected to the ciphering service. All actions for the ciphering activation process are finished in the course of the voice call.
In the related-art methods described with reference to FIGS. 2-4, only the network determines whether the ciphering activation process should be performed or not. Therefore, when the ciphering activation process is not initially preformed or data is not specific data, there is a disadvantage in that the ciphering activation process cannot be performed even when a user wants to cipher and transmit and/or receive important data through the network. As a result, the user's important data is susceptible to being wiretapped or abused externally. Thus, since voice and data can be transmitted without being ciphered, there is a serious disadvantage that the user's important information can be revealed to a third party.